Latching means for air-blast circuit breaker



Feb. 16, 1965 H. FORWALD 3,170,055

LATCHING MEANS FOR AIR-BLAST CIRCUIT BREAKER Filed Aug. 28, 1961 INVENTOR. Hank For MM aw wwwx United States Patent 4 V s Ciaims. or. 200-148 My invention relates to airblast circuit breakers and more specifically relates to a novel auxiliary structure for the movable contact of an air blast circuit breaker .which positively latc'hesthe movable contactin an engaged position so long as operating pressure is retained in the pneumatic operating system.

Accordingly, it is a primary object of this invention to provide a novel positive structure in the operating system of an air blast circuit breaker for gripping and retaining the movablecontact in a disengaged position so long as operating pressure is at a predetermined value.

A'further object of this invention is to provide a novel positive hold-open means for the movable contact of an air blast circuit breaker which is simple inconstruction and is highly reliable.

These and other objects of this invention will become apparent from a consideration of the following descrip tion taken in connection with the drawing which shows a cross-sectional view of a portion of an air blast interrupter provided with the invention. a

Referring to the drawing I have illustrated schematically in dottedlines the outline of a conductive pressure chamber first which carries the cooperating contacts of the interrupter. One wall of chamber 10 is partially illustrated as wall 11. A stationary contact 12 'is carried in insulated relationship with respect to chamber 19 as by connecting a contact 12 to a bushing which extends through chamber 10 (not shown) and carries a conductor there-through which serves as one terminal of the device. The other terminal of the device will be formed by the chamber 10. The chamber It is filled with a high pres sure gas such as air which is used to extinguish the are drawn between stationary contact 12 and a movable contact 13 Which is movable from the engaged position shown with respect to contact 12 and a disengaged position to e be described. g

The movable contact 13 is a tubular member which has an arcing contact 14 secured thereto through a spider 15. The movable contact 13 moves in an opening in the top of a cylinder 16 forming a second chamber and is electrically connected to cylinder 16 by appropriate sliding contacting means (not shown).

The cylinder 16 is secured within the wall 11 of the interrupter as shown by bolt means such as bolts 17 and 18, and defines an airtight seal to prevent the escape of high pressure air from within chamber 10. A spring biasing means 19 then seats against a shoulder of cylinder 16 as illustrated and a corresponding shoulder of contact 13as shown to bias contact'13 upwardly and toward engagement with respect to stationary contact 12. i

A blast valve 20 is then provided within cylinder 16 to normally seal the interior of the cylinder from the external atmosphere where, for example, blast valve 20 is provided with a flexible valve seat 21 which engages an annular surface of cylinder 16. Blast valve 20 is carried on an extension 22 of piston 23 whichmoves within cylinder 24. A spring 25 is'contained within cylinder 24to bias piston 23 and thus blast valve 20 downwardly so that the blast valve is normally seated as shown.

In accordance with the present invention the movable contact has a shaft 26 secured thereto which extends 3,110,055 Patented Feb. 16, 1965 ice downwardly and through an opening in extension 22 and blast valve 20. Shaft 26 is then terminated with a necked down portion 27 and an extending head 28, the shaft 26 being slideably movable within extension 22. Enlarged head 28 is then movable toward an engaged position with respect to rollers 29 and 30 which are carried on L-shaped arms 31 and 32 which are pivotally mounted at pivots 33 and 34 respectively. The inwardly extending arms of 'L-shaped members 31 and 32 are connected to springs 35 and 36 respectively of a piston 37 which is movable within a cylinder 38 in the bottom cap 39.

The two opposing arms 31 and 32 are so adapted that when the piston 37 is moved downwardly the rollers 29 and30 move .toward one another. Thus, when the enlargedhead 28 moves downwardly it will cam the rollers 29 and 30 away from one another by virtue of its sloping -front surfaces until the necked down portion 27 reaches "rollers 29 and 3t) whereupon the rollers 29 and 30 will snap into the necked'down portion 27 to grip and hold the shaft 26 andthus the movable contact 13 in the downwardly disposed position.

r This position will be retained until pressure on piston 37 is decreased so that the arms 31 and 32'move away from one another. and the biasing spring 19 can release necked down portion 27 from arms 31 and 32, and the contact 13 moved into its engaged position.

In operation and assuming that the interrupter is in the closed position shown, in order to move contact 13 to its disengaged position, air pressure is applied to conduit 40. Thiswill cause piston 23 to move upwardly so 'that blast valve 20 opens and the compressed air within cylinder" 16 and within the contact 13 may rapidly exhaust to the external air through blast air passages such as passage 41. This flow of air will cause a downward motion of contact 13 whereby air within chamber 10 will flow. through the orifice in the contact 13 to play upon the arc drawn between contacts 13 or 14- and stationary contact 12 to aid in extinguishing this arc. As the contact continues to move downwardly the shock absorbent layer 42 at the base of movable contact 13 engagesthe top of blast valve 20 and movable contact 13 moves the blast valve 2th to its seated position shown in the drawing. Thus, the blast action is stopped. once the movable contact assumes some predetermined open position. At the same time theshaft 26 has been moving downwardly with the neckedidown portion'27 of shaft 26 moving toward rollers 29 and 3h. The rollers 29and 30 have also been moved toward one another since, when pressure was ap plied to conduit 40 piston 37 is moved downwardly. Thus when the movable contact 13 assumes its lowermost position, the rollers 29 and 30 are seated in the necked down portion 27 and are biased toward a securing position. It is also noted that a controlled leak 43 is provided in piston 23 so that the high pressure fluid of conduit 40 can leak into the interior of chamber 24 to equalize the pressure upon either side of piston 23.

I To reclose movable contact 13, the pressure in conduit 40 is removed. This permits piston 37 to move upwardly to thereby relax the biasing force on arms 31 and 32, whereby spring 19 can move movable contact 13 toward the closed position.

In the foregoing, I have described my invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of my invention within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specific disclosure herein but only by the appending claims.

I claim:

1. In an air blast circuit breaker, a high pressure first chamber, a stationary contact within the first chamber,

. said first chamber having means forming a second chamher having a first opening into the first chamber and a second opening to free air, a blast valve normally closing said second opening, a movable contact movably mounted in the second chamber for movement between engaged and disengaged positions with respect to the stationary contact, a spring biasing said movable contact to engaged position, compressed-air-responsive means to move the blast valve to open position, means responsive to the opening of said blast valve to move the movable contact to disengaged position, gripping means for engaging the movable contact and holding it in disengaged position, and pressure-responsive means connected to the pressure 'in said compressed-air-responsive means for exerting a force on said gripping means tending to hold them in gripping position, the holding power of said gripping means being proportional to the force exerted thereon by said pressure-responsive means.

2. The device as set forth in claim 1 wherein said gripping means includes a pair of opposing levers.

3. The device as set forth in claim 2 wherein said movable contact has an extension extending therefrom engageable by said pair of opposing levers.

4. The device as set forth in claim 3, wherein the end of said extension has an enlarged head portion; and roller means at the respective ends of said opposing levers engageable with said enlarged head portion.

5. The device as set forth in claim 4 wherein the front of said enlarged head has camming surfaces to cam said rollers of said respective levers apart to permit said enlarged head to enter said opposed rollers.

References Cited by the Examiner -UNITED STATES PATENTS 2,856,480 10/58 Westerhoif 200-148 v 2,881,291 4/59 Forwald 200-148 2,936,355 5/60 Caswell 200l48 3,073,932 1/63 Schulz 200l48 FOREIGN PATENTS 532,467 11/21 France.

BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner. 

1. IN AN AIR BLAST CIRCUIT BREAKER, A HIGH PRESSURE FIRST CHAMBER, A STATIOANRY CONTACTT WITHIN THE FIRST CHAMBER, SAID FIRST CHAMBER HAVING MEANS FORMING A SECOND CHAMBER HAVING A FIRST OPENING INTO THE FIRST CHAMBER AND A SECOND OPENING TO FREE AIR, A BLAST VALVE NORMALLY CLOSING SAID SECOND OPENING, A MOVABLE CONTACT MOVABLY MOUNTED IN THE SECOND CHAMBER FOR MOVEMENT BETWEEN ENGAGED AND DISENGAGED POSITIONS WITH RESPECT TO THE STATIONARY CONTACT, A SPRING BIASING SAID MOVABLE CONTACT TO ENGAGED POSITION, COMPRESSED-AIR-RESPONSIVE MEANS TO MOVE THE BLADE VALVE TO OPEN POSITION, MEANS RESPONSIVE TO THE OPENING OF SAID BLAST VALVE TO MOVE THE MOVABLE CONTACT 